1. Field of the Invention
This invention relates to an electronic musical instrument which has a keyboard device capable of expressing sounds having wide dynamic ranges.
2. Prior Art
As an electronic musical instrument of this kind, there has been conventionally well known one which has two or more switches which are disposed to be closed at different times (hereinafter referred to as "contact times") from each other when a corresponding key is depressed, and detects the difference between the contact times to calculate therefrom the velocity of depression of the key (hereinafter referred to as "key depression velocity") to thereby realize a sound having a dynamic range corresponding to the calculated key depression velocity, i.e. the key depression strength.
However, according to the above conventional electronic musical instrument, it is difficult to accurately detect values of the key depression strength larger than f (forte).
More specifically, referring to FIG. 1 showing a characteristic curve representing the relationship between the key depression strength and the contact time difference, the characteristic curve has a sharp gradient relative to the time difference in a key depression strength region less than f (forte) so that the key depression strength can be easily determined from the contact time difference, whereas the curve has a gentle gradient in a key depression strength region larger than f (forte) so that the key depression strength cannot be easily accurately determined from the contact time difference due to a small change in the contact time difference relative to a change in the key depression strength. As a result, it is difficult to express a sound from values of the key depression strength exceeding f (forte).